AP Chemistry Semester Test (1)

C2H6O

A 23.0g sample of a compound contains 12.0g of C, 3.0g of H, and 8.0g of O. Which of the following is the empirical formula of the compound?

SF4

A compound contains 30. percent sulfur and 70. percent fluorine by mass. The empirical formula of the compound is

Peak X, because F has a greater nuclear charge than C has.

A sample containing atoms of C and F was analyzed using x-ray photoelectron spectroscopy. The portion of the spectrum showing the 1s peaks for atoms of the two elements is shown above. Which of the following correctly identifies the 1s peak for the F atoms and provides an appropriate explanation?

SF6

A sample of a compound contains 3.21 g of sulfur and 11.4 g of fluorine. Which of the following represents the empirical formula of the compound?

CH5N

A sample of a compound that contains only the elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45.0 g of H2O, and some NO2 . A possible empirical formula of the compound is

3,4,6,7

A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?

MgO

According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen?

Ba

Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine with atoms of F in the same ratio?

Mg3X2

Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is

242 pm, 419 kJ/mol

Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?

X2(SO4)

Based on the ionization energies of element X given in the table above, which of the following is most likely the formula of the compound formed between element X and SO42- ?

X2O3

Based on the ionization energies of element X given in the table above, which of the following is most likely the empirical formula of an oxide of element X?

C4H8

Complete combustion of a sample of a hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound?

S

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons

Ga

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel

N2

Each set of lettered choices below refers to the numbered statement immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2

Cs

Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. (A) Cs (B) Ag (C) Pb (D) Br (E) Se

The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.

For element X represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies?

1.2 x 10^24

How many carbon atoms are contained in 2.8 g of C2H4 ?

different because S has a greater number of electron domains (regions of electron density) surrounding it than C has

Lewis electron-dot diagrams for CO2 and SO2 are given above. The molecular geometry and polarity of the two substances are

CH4 < SiCl4 < SF4

On the basis of the information above, which of the following arranges the binary compounds in order of increasing bond polarity?

CBr4

The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of the periodic properties, which of the following compounds can most likely be used as a fire-resistant chemical?

trigonal planar

The geometry of the SO3 molecule is best described as

sp2

The hybridization of the carbon atoms in the molecule represented above can be described as

Mg with 14 neutrons

The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26 amu represents an isotope of which of the following elements?

Zr

The mass spectrum of an average sample of a pure element is shown in the figure above. Which of the following is the identity of the element?

Ga

The mass spectrum of an element is represented above. Which of the following is most likely the identity of the element?

The atomic mass of X is between 90 and 92.

The mass spectrum of element X is presented in the diagram above. Based on the spectrum, which of the following can be concluded about element X?

B

The mass spectrum of the element Sb is most likely represented by which of the following?

Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen atom. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?

The electrons in the 2p sublevel have the smallest binding energy.

The photoelectron spectrum for the element nitrogen is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom?

Reheat the sample until its mass is constant.

To determine the percentage of water in a hydrated salt, a student heated a 1.2346 g sample of the salt for 30 minutes; when cooled to room temperature, the sample weighed 1.1857 g. After the sample was heated for an additional 10 minutes and again cooled to room temperature, the sample weighed 1.1632 g. Which of the following should the student do next?

sp

What is the hybridization of the carbon atoms in a molecule of ethyne, represented above? H - C ≡ C - H

10.

When a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 ⋅ H2O(s), is heated, H2O (molar mass 18 g) is driven off. The mass of the anhydrous Na2SO4(s) (molar mass 142 g) that remains is 1.42 g. The value of x in the hydrate is

HfCl3

When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound?

F- has a larger nuclear charge than O2- has.

Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion?

The first ionization energy of Na is less than that of Mg.

Which of the following best helps to explain why Na(s) is more reactive with water than Mg(s) is?

NH4Cl

Which of the following compounds contains both ionic and covalent bonds?

The atomic radius of Cl is smaller than that of S because Cl has a larger nuclear charge than S does.

Which of the following correctly compares periodic properties of two elements and provides an accurate explanation for that difference?

Mo

Which of the following elements has the mass spectrum represented above?

1s2 2s2 2p6 3s1

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

Sr2+

Which of the following ions has the same number of electrons as Br - ?

1s2 2s2 2p6 3s1 3p1

Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy?

1s2 2s2 2p6

Which of the following is the ground-state electron configuration of the F− ion?

1s2 2s2 2p6 3s2 3p6 3d4

Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25)